I suggest adding P2.5 and P10 values for all cities. Currently, only Beijing and Shanghai have P2.5 values. I have tried to get my hands on airborne particulate levels in Wuhan for years. Thank you for this website!

There is a new official source of data for Poland - http://powietrze.gios.gov.pl/pjp/current. It aggregates data from all the regional sources (WIOŚ) you're currently using. The API is currently undocumented but it should be quite easy to get the data using web scraping of the main page or via JSON used by the charts.